[netstack] Refactor common utils out of netstack to socket package.

Moved AddressAndFamily() and ConvertAddress() to socket package from netstack.
This helps because these utilities are used by sibling netstack packages.

Such sibling dependencies can later cause circular dependencies. Common utils
shared between siblings should be moved up to the parent.

PiperOrigin-RevId: 345275571

1 files changed, 175 insertions, 0 deletions

diff --git a/pkg/sentry/socket/socket.go b/pkg/sentry/socket/socket.go
index fd31479e5..9049e8a21 100644
--- a/pkg/sentry/socket/socket.go
+++ b/pkg/sentry/socket/socket.go
@@ -18,6 +18,7 @@
 package socket
 
 import (
+	"bytes"
 	"fmt"
 	"sync/atomic"
 	"syscall"
@@ -35,6 +36,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -460,3 +462,176 @@ func UnmarshalSockAddr(family int, data []byte) linux.SockAddr {
 		panic(fmt.Sprintf("Unsupported socket family %v", family))
 	}
 }
+
+var sockAddrLinkSize = (&linux.SockAddrLink{}).SizeBytes()
+var sockAddrInetSize = (&linux.SockAddrInet{}).SizeBytes()
+var sockAddrInet6Size = (&linux.SockAddrInet6{}).SizeBytes()
+
+// Ntohs converts a 16-bit number from network byte order to host byte order. It
+// assumes that the host is little endian.
+func Ntohs(v uint16) uint16 {
+	return v<<8 | v>>8
+}
+
+// Htons converts a 16-bit number from host byte order to network byte order. It
+// assumes that the host is little endian.
+func Htons(v uint16) uint16 {
+	return Ntohs(v)
+}
+
+// isLinkLocal determines if the given IPv6 address is link-local. This is the
+// case when it has the fe80::/10 prefix. This check is used to determine when
+// the NICID is relevant for a given IPv6 address.
+func isLinkLocal(addr tcpip.Address) bool {
+	return len(addr) >= 2 && addr[0] == 0xfe && addr[1]&0xc0 == 0x80
+}
+
+// ConvertAddress converts the given address to a native format.
+func ConvertAddress(family int, addr tcpip.FullAddress) (linux.SockAddr, uint32) {
+	switch family {
+	case linux.AF_UNIX:
+		var out linux.SockAddrUnix
+		out.Family = linux.AF_UNIX
+		l := len([]byte(addr.Addr))
+		for i := 0; i < l; i++ {
+			out.Path[i] = int8(addr.Addr[i])
+		}
+
+		// Linux returns the used length of the address struct (including the
+		// null terminator) for filesystem paths. The Family field is 2 bytes.
+		// It is sometimes allowed to exclude the null terminator if the
+		// address length is the max. Abstract and empty paths always return
+		// the full exact length.
+		if l == 0 || out.Path[0] == 0 || l == len(out.Path) {
+			return &out, uint32(2 + l)
+		}
+		return &out, uint32(3 + l)
+
+	case linux.AF_INET:
+		var out linux.SockAddrInet
+		copy(out.Addr[:], addr.Addr)
+		out.Family = linux.AF_INET
+		out.Port = Htons(addr.Port)
+		return &out, uint32(sockAddrInetSize)
+
+	case linux.AF_INET6:
+		var out linux.SockAddrInet6
+		if len(addr.Addr) == header.IPv4AddressSize {
+			// Copy address in v4-mapped format.
+			copy(out.Addr[12:], addr.Addr)
+			out.Addr[10] = 0xff
+			out.Addr[11] = 0xff
+		} else {
+			copy(out.Addr[:], addr.Addr)
+		}
+		out.Family = linux.AF_INET6
+		out.Port = Htons(addr.Port)
+		if isLinkLocal(addr.Addr) {
+			out.Scope_id = uint32(addr.NIC)
+		}
+		return &out, uint32(sockAddrInet6Size)
+
+	case linux.AF_PACKET:
+		// TODO(gvisor.dev/issue/173): Return protocol too.
+		var out linux.SockAddrLink
+		out.Family = linux.AF_PACKET
+		out.InterfaceIndex = int32(addr.NIC)
+		out.HardwareAddrLen = header.EthernetAddressSize
+		copy(out.HardwareAddr[:], addr.Addr)
+		return &out, uint32(sockAddrLinkSize)
+
+	default:
+		return nil, 0
+	}
+}
+
+// BytesToIPAddress converts an IPv4 or IPv6 address from the user to the
+// netstack representation taking any addresses into account.
+func BytesToIPAddress(addr []byte) tcpip.Address {
+	if bytes.Equal(addr, make([]byte, 4)) || bytes.Equal(addr, make([]byte, 16)) {
+		return ""
+	}
+	return tcpip.Address(addr)
+}
+
+// AddressAndFamily reads an sockaddr struct from the given address and
+// converts it to the FullAddress format. It supports AF_UNIX, AF_INET,
+// AF_INET6, and AF_PACKET addresses.
+//
+// AddressAndFamily returns an address and its family.
+func AddressAndFamily(addr []byte) (tcpip.FullAddress, uint16, *syserr.Error) {
+	// Make sure we have at least 2 bytes for the address family.
+	if len(addr) < 2 {
+		return tcpip.FullAddress{}, 0, syserr.ErrInvalidArgument
+	}
+
+	// Get the rest of the fields based on the address family.
+	switch family := usermem.ByteOrder.Uint16(addr); family {
+	case linux.AF_UNIX:
+		path := addr[2:]
+		if len(path) > linux.UnixPathMax {
+			return tcpip.FullAddress{}, family, syserr.ErrInvalidArgument
+		}
+		// Drop the terminating NUL (if one exists) and everything after
+		// it for filesystem (non-abstract) addresses.
+		if len(path) > 0 && path[0] != 0 {
+			if n := bytes.IndexByte(path[1:], 0); n >= 0 {
+				path = path[:n+1]
+			}
+		}
+		return tcpip.FullAddress{
+			Addr: tcpip.Address(path),
+		}, family, nil
+
+	case linux.AF_INET:
+		var a linux.SockAddrInet
+		if len(addr) < sockAddrInetSize {
+			return tcpip.FullAddress{}, family, syserr.ErrInvalidArgument
+		}
+		binary.Unmarshal(addr[:sockAddrInetSize], usermem.ByteOrder, &a)
+
+		out := tcpip.FullAddress{
+			Addr: BytesToIPAddress(a.Addr[:]),
+			Port: Ntohs(a.Port),
+		}
+		return out, family, nil
+
+	case linux.AF_INET6:
+		var a linux.SockAddrInet6
+		if len(addr) < sockAddrInet6Size {
+			return tcpip.FullAddress{}, family, syserr.ErrInvalidArgument
+		}
+		binary.Unmarshal(addr[:sockAddrInet6Size], usermem.ByteOrder, &a)
+
+		out := tcpip.FullAddress{
+			Addr: BytesToIPAddress(a.Addr[:]),
+			Port: Ntohs(a.Port),
+		}
+		if isLinkLocal(out.Addr) {
+			out.NIC = tcpip.NICID(a.Scope_id)
+		}
+		return out, family, nil
+
+	case linux.AF_PACKET:
+		var a linux.SockAddrLink
+		if len(addr) < sockAddrLinkSize {
+			return tcpip.FullAddress{}, family, syserr.ErrInvalidArgument
+		}
+		binary.Unmarshal(addr[:sockAddrLinkSize], usermem.ByteOrder, &a)
+		if a.Family != linux.AF_PACKET || a.HardwareAddrLen != header.EthernetAddressSize {
+			return tcpip.FullAddress{}, family, syserr.ErrInvalidArgument
+		}
+
+		// TODO(gvisor.dev/issue/173): Return protocol too.
+		return tcpip.FullAddress{
+			NIC:  tcpip.NICID(a.InterfaceIndex),
+			Addr: tcpip.Address(a.HardwareAddr[:header.EthernetAddressSize]),
+		}, family, nil
+
+	case linux.AF_UNSPEC:
+		return tcpip.FullAddress{}, family, nil
+
+	default:
+		return tcpip.FullAddress{}, 0, syserr.ErrAddressFamilyNotSupported
+	}
+}